Most automatic machinery operates in cyclical fashion, and for production control purposes it is important to be able to determine the number of cycles being performed during an operating period as a measure of work performed and to indicate when work is not being performed so that corrective action may be taken. The present invention provides for such production control by counting load current pulsations in an electrical supply to provide a count of the number of functions performed by the driven device, such as counting the number of picks of a loom during an operating period.
As most electrically powered automatic machinery is driven by alternating current electric motors, operational cycles have been counted heretofore by detecting the presence or absence of power surges in the alternating current supply to a motor while monitoring the alternations of the current supply but without regard to the number of load pulsations during a period of loading. The detection then creates a continuous signal during continuance of the loading, which signal is applied to an integrating calibrated counter or computer which estimates the number of work cycles performed by multiplying the accumulated time during which the signal is received by an assumed cyclic rate of the machinery. Cycle counting has also been performed mechanically by counters connected to machine shafts rotating in proportional relation to work cycles, electromechanically or electrically through switches operated by cams on such shafts or other working parts, or electrically through proximity switches associated with such shafts or parts.
While these prior art counting devices are serviceable, they are less than desirable. For example, the continuous power surge indicators do not actually count cycles, but must be calibrated on the basis of an independent reading of a representative cyclic rate of the machinery, which may differ from machine to machine, and may vary in a given machine according to electrical supply voltages, machine maintenance, workpiece material or other variables. The other aforementioned counters are subject to mechanical maintenance and breakdowns, they clutter up the machinery, they are expensive, some are subject to cheating, and the mechanical ones retain their data at the machine rather than transmit it to a central collection and control point.
The present invention utilizes the aforementioned power surges by taking the detection of pulsations of cyclical loading, as indicated by a continuous signal in the prior art devices, and monitoring these individual pulsations to provide an indication of the individual cycles that are then counted to provide a precise, rather than calibrated, reading of the number of work cycles performed during a particular work period. Thus, the method of the present invention can be used with solid state electronic apparatus hardly subject to breakdown, requiring no maintenance, and self-powered by the current pulsations it monitors. It may be applied to a variety of machines and to multiple installations of similar machines without individual calibration and may be applied internally of existing control apparatus and is inexpensive to install. It is virtually cheatproof and ideally suited to create signals for transmission to a remote central counting, data collection, computer center, or control point. The novel method of the present invention utilizes the pulse detector in a new way in order to create a discrete signal corresponding to each pulsation for use in counting the pulsations, and such a capability has not existed heretofore.